Prostate epithelial stem cells (green) may trigger cancer
A newly identified type of stem cell may cause some cases of prostate cancer, research on mice suggests.
The cells, found among those which line the inner cavity of the prostate gland, can produce copies of themselves, and other, more mature cell types.
But researchers showed that when the cells were deliberately mutated by switching off a tumour suppressor gene they rapidly formed tumours.
The Columbia University study appears in the journal Nature.
Prostate cancer is the most common cancer in men in the UK.
Each year around 34,000 men are diagnosed with the disease, and around 10,000 die from it.
Stem cells, the body's master cells which can form many different types of tissue, have previously been implicated in other forms of cancer, such as leukaemia.
Their possible role in prostate cancer has been the subject of speculation for many years.
The cells have a long lifespan in the prostate and exist to generate new tissue, so in theory if they mutate and start to grow in an unregulated way they have the potential to be very damaging.
The newly identified cells - a type of luminal epithelial stem cell - do not rely on androgens - the male sex hormones that control prostate growth - to thrive.
This may give a clue as to why prostate cancer often becomes resistant to treatments designed to regulate these androgens in the later stages of the disease.
However, researcher Dr Michael Shen stressed more work was needed to establish whether the cells existed in humans, and could trigger cancer.
He said: "While there does appear to be increasing evidence suggesting that normal stem cells may serve as an origin for cancer, the 'cancer stem cell' model remains far from proven, especially in solid tumours such as prostate.
"In principle, therapies directed at putative cancer stem cells may be beneficial, but this field is still at a very early stage."
Dr Helen Rippon, of The Prostate Cancer Charity, said: "It will be some time before we know if or how these findings apply to humans.
"However, understanding the very earliest stages of prostate cancer development and the cells involved is critical if we are to develop better ways to detect and treat the disease."
Dr Owen Sansom, a stem cell researcher from Cancer Research UK's Beatson Institute for Cancer Research, said the study raised the possibility of developing new treatments to tackle prostate cancer that was resistant to hormone-based therapy.
Sex disease link
In a separate study, a team from Harvard School of Public Health has found a strong association between a common sexually transmitted infection, Trichomonas vaginalis, and advanced lethal prostate cancer.
The National Cancer Institute study suggests the infection could be a source of inflammation which might trigger the cancer.
Trichomonas vaginalis infects an estimated 174 million people globally each year, but in up to three-quarters of infected men it produces no obvious symptoms.
Researchers analysed blood samples from 673 men with prostate cancer, comparing them with a similar number of samples from men who were free from the disease.
They found Trichomonas vaginalis infection was associated with a more than two-fold increase in the risk of prostate cancer that was advanced stage at diagnosis, and a nearly three-fold increase in prostate cancer that would result in death.